PROPERTIES OF ENDODONTIC HAND INSTRUMENTS USED IN ROTARY MOTION .2. INSTRUMENTATION OF CURVED CANALS

The shaping abilities of nickel-titanium K-files, stainless steel ream ers, K-files, and flexible stainless steel instruments with convention al cutting tips and with modified noncutting tips were investigated un der standardized conditions using a computer-driven testing device sim ulating the clinical use of the instruments, Simulated root canals wit h a 42-degree curvature were sequentially enlarged from #15 to #35, Un desirable changes in the canal shape as a result of instrumentation oc curred in all cases, None of the instruments were able to remove mater ial on the whole length of the inner side of the curvature, whereas al l instruments removed material on the whole length of the outer side o f the curvature, resulting in slight to severe bulging, The extent of undesirable changes in the canal shape depended typically on the type of instrument used, Best instrumentation results were obtained with fl exible instruments with noncutting tips.