An evaluation of the Canal Master, balanced force, and step-back techniques.

The step-back (SB), balanced-force (BF) , and Canal Master (CM) instrumentation techniques were compared in 53 mesial canals of mandibular molars using two different instrument types: Flex-R and CM. Canal angulation changes from preoperative to postrotary and postinstrumentation were measured using the Schneider technique (ST) and the long-axis technique (LAT). Instrumentation times were recorded, and then the roots were sectioned at 1, 3, and 5 mm from the apex. Measurements were made of the minimal remaining root structures and canal diameter. Rotary instrumentation resulted in a average loss of curvature of 2.37 degrees, as measured by the ST. The ST showed significant changes in canal angulation between CM (-7.74 degrees) and SB (-5.28 degrees) groups, with p < 0.05. LAT showed significant changes for CM versus BF and SB (p<0.001), with a mean change in angulation of -7.69 degrees, -1.68 degrees, and _0.1 degrees respectively. The BF technique (5.5) was significantly faster than either SB (7.1 min) or CM (8.3 min), with p < 0.05. The remaining mesial-distal root structure at all levels was similar among groups.