Effect of Handpiece Load on the Cutting Efficiency of Dental Burs

A reproducible test regimen was developed to evaluate the cutting efficiency (CE) of diamond dental burs against a machinable glass ceramic, Macor, under three different loads. The test jig used an ultra-highspeed dental handpiece in a frictionless bearing so that the pressure applied to the contact interface between the dental bur and the cutting substrate could be controlled. Loads ranging from 44 to 183 g were used. CE depends on both bur rugosity and the handpiece load. The load used by most dentists, about 100 g at the bur tip, appears to be optimal in that at lower loads CE is reduced, whereas a marked increase in load has no effect for medium-grit burs. With coarse-grit burs, however, increased handpiece pressure raises the CE; it is uncertain what effect this has on the dental pulp. CE also appears to be dependent upon debris accumulation between the diamond particles and wear of diamond.