TORSIONAL AND METALLURGICAL PROPERTIES OF ROTARY ENDODONTIC INSTRUMENTS .2. STAINLESS-STEEL GATES GLIDDEN DRILLS

A laboratory study was performed on stainless steel Gates Glidden drills to determine their torsional and metallurgical properties. Samples of #1 to #6 drills from the two manufacturers that distribute these instruments in the United States were tested in incremental and continuous clockwise torsional loading by using a digital torque meter. The values of mean torque at fracture obtained with these tests generally showed no statistically significant differences for the same drill size and a given manufacturer. However, it was not possible to completely evaluate drill sizes #5 and #6 because the torsional moments developed during testing exceeded the capacity of the test instrument. Scanning electron microscope examination confirmed the occurrence of ductile torsional fracture processes, which were evident from visual observation of the instruments after fracture. This study is part of a continuing investigation to establish standards for all rotary endodontic instruments.