FIG. 3.

SEM images of an experimental biofilm and bactericidal effect of hydroxyl radicals on S. mutans in the biofilm. (A) It was observed that the biofilm was composed of extracellular matrix and multiple cell layers. The right image shows a higher magnification of the outlined area in the left image. The solid arrow shows extracellular matrix covering the cluster of bacterial cells, and the dotted arrow shows the multiple cell layers. (B) The biofilm contained approximately 10⁸ CFU/well, as shown by H(−)L(−). The H(+)L(+) condition (hydroxyl radial disinfection system) could kill S. mutans in biofilm with a ≥5-log reduction within 3 min. Each bar represents the mean of triplicate determinations.