New carbide burs that are placed on a bur block can be subjected to multiple steam autoclaving cycles prior to their first use. The decision to discard a bur before or during cavity preparation is a subjective one based on operator expectations and experience. This study examined the durability of carbide burs after multiple autoclaving cycles by judging not only their initial sharpness but also their ability to maintain sharpness throughout a cavity preparation. Five experienced operators were given a set of No. 330 carbide burs that had been separated into five blind categories: those not autoclaved at all and those that had been autoclaved one, two, five, or 10 times. Each operator judged the cutting effectiveness of each bur by making an initial plunge cut through the enamel of a freshly extracted tooth. After the initial plunge cut, each operator used the same set of burs to complete an occlusal cavity preparation in molar models fabricated from composite restorative material. Each operator was asked to examine the burs for any visual deterioration and to rate the cutting ability of each bur. The burs were also examined for wear under a scanning electron microscope. Based on the results, this study concluded that up to 10 autoclaving cycles did not significantly affect the perception of either initial sharpness or the bur's effectiveness while completing the preparation.