Figure 3. Roughness distribution for (a) Virgin tooth, (b) Crest^TM toothpaste-polished, (c) NuPro^TM-polished, and (d) slurry-polished tooth surface. The average and standard deviation values are: 21 ± 6 nm (a), 22 ± 4 nm (b), 25 ± 5 nm (c), and 2.4 ± 1.4 nm (d).