Evaluation of hand instruments used in operative dentistry: hardness and sharpness

Four brands of dental instruments were evaluated for Knoop hardness in this study. Enamel hatchets and hoes made from two brands of carbon steel and two brands of stainless steel were tested as received and after 10, 30, and 50 cycles of dry heat or steam autoclave sterilization. Results indicated an initial reduction in hardness in the carbon steels after 10 cycles, then no further hardness deterioration. Both of the stainless steels tested were significantly softer than the two carbon steels before and after sterilization. SEM evaluation of two brands of carbon-steel enamel hatchets and two brands of stainless-steel enamel hatchets before and after planing enamel revealed more rapid dulling of blade edges on the stainless-steel instruments than on the carbon-steel instruments.