PROPERTIES OF ENDODONTIC HAND INSTRUMENTS USED IN ROTARY MOTION .3. RESISTANCE TO BENDING AND FRACTURE

Bending and torsional properties of 24 different types of nickel-titan ium K-files, titanium-aluminium K-files and reamers, conventional stai nless steel K-files and reamers, and flexible stainless steel instrume nts were investigated corresponding to ISO 3630-1 by determination of the bending moment on the one hand and the torque and angular deflecti on on the other, Numbers 15, 25, and 35 instruments were tested with a sample size of 10 instruments for each type and size, In ascending or der of bending moment the instruments ranked: nickel-titanium K-files, titanium-aluminium K-files and reamers, flexible stainless steel inst ruments, conventional stainless steel K-files, and reamers, Nickel-tit anium, titanium aluminium, and flexible stainless steel instruments di splayed lower torque values than conventional stainless steel K-files and reamers, The average angular deflection ranged from 380 degrees (# 15 reamer) to 2370 degrees (#35 K-file), Overall, the fracture risk of the instruments tested in this study was comparably low.