Investigation of variable factors in drilling bone.

Experiments were conducted to investigate the pressures that are exerted on drills during the preparation of bone. Twenty operators used six different types of drills at high and low speeds to prepare standardized holes and slots in animal bone. The peak vertical forces exerted varied between 5.98 and 24.32 newtons (x = 12.45 newtons). The mean vertical forces varied between 4.22 and 18.93 newtons (x = 9.16 newtons). Spear point and twist drills were associated with significantly lower operating pressures and shorter operating times than round and fissure burs. These differences, however, were much less than the interoperator variations.