A method to assess rotary nickel-titanium files

A number of studies have assessed the physical properties and durability of rotary nickel-titanium files. This study proposes a method that will permi t this to be done in a controlled manner. Files of 0.04 taper; 25 mm in len gth; and in ISC sizes 25, 30, and 35 were each used four times in plastic b locks. The canal in the block had a working length of 17 mm; 30 degrees cur vature; 15 mm radius of curvature; size 20 at the apex; and the curve began at 8 mm from the orifice of the canal. The irrigant used was Glyde(R) An e lectric handpiece was configured to rotate at 200 rpm and secured to the te sting device, which also held the plastic block, The testing device control led the depth of penetration at 17 mm; the load was at 8 N and the rate of penetration was at 120 mm/min. Controls were not subjected to use. Torsiona l moment (N-cm) and angular deflection (degrees) at failure were determined on a Torsiometer\Memocouple. Data (n = 5) were analyzed by analysis of var iance. Tukey-Kramer intervals at the 0.05 significance level were determine d. Torsional moment significantly increased with an increase in size. Torsi onal moment also significantly increased for used instruments, compared wit h controls. Angular deflection had a range of 480 degrees to 810 degrees fo r the instruments tested.