Breaking the fluoride diffusion barrier with combined dielectrophoresis and AC electroosmosis

To compare the deposition of fluoride particles into bovine enamel by diffusion (n = 20); dielectrophoresis (DEP) at 10 Hz and 5000 Hz (n = 10); and DEP (10 Hz and 5000 Hz) combined with AC electroosmosis (ACEO) at 400 Hz (DEP/ACE) (n = 10).

Fluoride particle movements induced at 10, 400, and 5000 Hz frequencies, were analyzed with light microscopy and stack imaging in real time. Fluoride concentrations were measured at various enamel depths using wavelength dispersive spectrometry. Results were analyzed by ANOVA/Student-Newman-Keuls post hoc (P = 0.05).

Fluoride levels in teeth treated with DEP were significantly higher than diffusion at depths 10 and 20 microm. DEP and diffusion were relatively ineffective at greater depths. The highest fluoride concentrations at 10, 20, and 50 microm depths were found in the DEP/ACE group. After 20 minutes, DEP/ACE increased fluoride uptake by 600% at 50 microm and 400% at 100 microm compared to baseline levels (P < 0.05). Fluoride particle movement was induced by negative DEP at 10 Hz; positive DEP at 5000 Hz; and ACEO at 400 Hz frequency.