This in vitro study was carried out to compare the cutting efficiency of diamond grinders
on zirconia and resin-based composite materials. Grinders were employed with a special holder
for the handpiece to apply a constant load (160 g) for resin-based composite (8 cuts, 40 s each) and
zirconia materials (4 cuts, 5 min each; n = 10 for each material and grinder). To assess the efficiency of
the grinders, weight measurements of the material were taken before and after the grinding process.
Scanning electron micrographs were captured for instrument surfaces before and after testing and
for the resulting surface of the materials. In the resin-based composite group, there were significant
differences in weight removal between the burs for both the baseline (first cut; p = 0.009) and removal
after the eighth cut (p = 0.049). Statistically significant decreases in weight removal compared to
the baseline values were noted for the third, fourth, sixth, and seventh steps (p ≤ 0.046). For the
zirconia group, significant differences existed in weight removal between the burs for the baseline
(first cut; p < 0.001) and removal after the fourth cut (p < 0.001). A significant positive correlation
was observed between removal and the number of cuts (Pearson: 0.673; p < 0.001). A statistically
significant decrease in removal compared to the respective baseline value was found for the fourth
step (p = 0.006). The initial wear removal and durability significantly differed between the grinders
used on resin-based composite and zirconia. Achieving comparable weight removal took five times
longer when grinding zirconia compared to the resin-based composite.