Accuracy of the DTC torque control motor for nickel-titanium rotary instruments

To determine the torque output and examine the accuracy of five identical DTC torque control (DTC) motors.

Torque settings on the DTC motors for the.04 ISO ProFile nickel-titanium (NiTi) rotary instruments were evaluated at 350 r.p.m. A modification of the ANSI/ADA Specification No. 28 setup for the evaluation of torsional properties of endodontic instruments was used. A handpiece was attached to the motor and gripped with a vice. An.07 Orifice Shaper, size 50, was inserted in the handpiece. The instrument tip was clamped in a chuck connected to a torque sensor. The motor was then activated to rotate the instrument in a clockwise direction until reversal of the rotation occurred. The actual torque generated at the reversal of the rotation was recorded. Ten tests were carried out at each torque setting. A new Orifice Shaper was used for each test. The means of the actual torque values generated by the motors at the different torque settings were compared with the torque values claimed by the manufacturer and analysed using analysis of variance and the Student's t-test (alpha = 0.05).

The actual torque values were significantly higher than the torque preset on the motors (P < 0.0001) and did not differ significantly among the motors (P > 0.05).

The actual torque deviated from the preset torque and was higher than the reported torque at fracture of several NiTi rotary instruments. The usefulness of these motors is questionable.