Physical dimensions and torsional properties of rotary endodontic instruments. 1. Gates Glidden drills.

A laboratory study was performed on Gates Glidden drills to determine their physical dimensions and torsional properties. Five samples of sizes #1 to #6 drills from two brands distributed in the United States were measured for physical dimensions. Five samples of the most commonly used sizes #1, #2, and #3 drills from these two brands were tested at failure in both the clockwise and counterclockwise directions using an analog torque meter. The values for the bur head dimensions of both brands correspond closely to those established by the ISO. The mean values for torque at failure for both the clockwise and counterclockwise directions showed no statistically significant difference for each brand-size combination. However, some instrument groups had separation or fracture sites near the bur head, while other groups underwent failure near the hand-piece end. This study is the first part of a continuing investigation to establish standards for rotary endodontic instruments.