Background. Tooth preparation requires safe, efficient and rapid cutting, and diamond burs routinely are used for extracoronal preparation and gross tooth reduction. Coarser-grit diamond burs often are used for gross tooth reduction, with tooth surface finishes being sacrificed for the presumed greater cutting rates, or CRs, of the coarser diamond burs. The authors compared the CRs of medium-, coarse- and super–coarse-grit diamond burs.
Methods. The authors used a self-contained dental treatment system with digitally controlled handpiece speed, torque and water flow rate to cut a machinable glass ceramic cutting substrate with medium-, coarse- and super–coarse-grit diamond burs from the same manufacturer under a load of 147.5 grams (0.9 kilonewton at the bur tip) and a coolant flow rate of 22 milliliters per minute. They made three cuts through 13-millimeter bars of the cutting substrate with six diamond burs of each grit size. They determined CRs as the transection time per millimeter and analyzed CR data by one-way analysis of variance and post hoc Scheffé tests.
Results. The authors found no statistically significant difference in CR (P > .05) between the three diamond bur grit sizes for the first (13 mm) cuts. When they compared the three cuts (39 mm total cut length), they found no difference (P > .05) between CRs for coarse- and super–coarse-grit diamond burs, but they did find that the super–coarse-grit diamond burs cut faster than the medium-grit diamond burs (P < .01).
Conclusion. Differences in CR for the three diamond bur grit sizes are due to the greater decrease in CR for the medium-grit diamond burs (50 percent) compared with the CRs of the coarse- and super–coarse-grit diamond burs (35 percent and 25 percent, respectively) over the total cutting period.
Clinical Implications. Coarser-grit diamond burs may be useful for extensive gross tooth preparations, but dental professionals should be aware of the associated effects of the coarser grit on surface finish, heat generation and enamel damage.
