Relationship between file size and stiffness of stainless steel instruments

The purpose of this study was to evaluate the relationship existing between file size and stiffness for three endodontic files of different cross-sections. Three groups of instruments were tested: Flexofiles from the Maillefer company, K Files and K-Flex from the Kerr company. Flexofiles have a triangular cross-section, K Files a square cross-section, and K-Flex instruments a rhombus cross-section from size 15 to size 40. For each group, 10 files from size 15 to size 40 were compared according to ANSI/ADA specification N degrees 28 for bending moment evaluation. There was a statistical difference between the three groups: the square cross-section K files presented a larger bending moment than the rhombus cross-section K Flex, which presented a higher bending moment than the triangular cross-section Flexofiles. There was an exponential relationship between file size and bending moment.