The effects of Canal Master, Flex-R, and K-Flex instrumentation on root canal configuration

The purpose of this study was to compare the Canal Master instrument and instrumentation technique (CM/CMI) to Flex-R files used with a "balanced force" technique (FR/BF) and K-Flex files used with a step-back filing technique (KF/SB). Thirty-six root canals in extracted human mandibular molars were equally divided into three groups. The roots were sectioned, then photographed and evaluated before and after instrumentation. Evaluation included canal shape, direction and extent of transportation, amount of dentin removed, and centering ability. Canal Master instrumentation and Flex-R/balanced force techniques both produced more round preparations than the K-Flex/step-back. All three techniques resulted in canal transportation, although to varying degrees. Flex-R/balanced forces and Canal Master instrumentation transported very little up to a #30, and Canal Master instrumentation transported significantly less after the #45 instrument at mid-root. K-Flex/step-back removed the most dentin while Flex-R/balanced force removed the least in the apical sections and Canal Master instrumentation removed the least at mid-root. The ability of Canal Master instrumentation to keep instruments centered in the canals was significantly better than for K-Flex/step-back.