Figure 2. Mean fluoride concentration profiles throughout the depth of plaque biofilms (n = 6, error bars show ± SEM). (a) Biofilms exposed to NaF for 30 sec, ± wash in saliva-like solution. (b) Biofilms exposed to NaF for 120 sec, ± wash in saliva-like solution. (c) Unexposed controls, and biofilms exposed to NaF for 30 min.