Figure 4. A series of AFM images (a–c) of a slurry-polished tooth surface with adherent S. mutans. Image (a) was taken after initial scans; (b) shows the bacterial adhesion after approximately 1 min; (c) demonstrates the bacteria remaining at the end of the scanning series. A schematic of the rastering mode is also shown (d). During the rastering, the AFM probe moves quickly from left to right, while slowly scanning up and down. The bacteria attached to the surface can be removed by the lateral force of the AFM probe. (a) Relatively small area of the tooth surface, which was initially covered with a continuous layer of bacteria, and was just exposed after the initial bacterial removal. (b) Shows the bacteria survived after approximately 1 min. (c) Demonstrates the remaining bacteria at the end of a two-minute scan series. White asterisks (boxes) indicate areas with roughness of 1.8–2.4 nm (5.0–5.5 nm). During scanning, the bacteria were removed from the lower-roughness areas (marked with asterisks) first, and from higherroughness areas (marked with boxes) last. Scale bars are 4 microns.