Dielectrophoretic transport of fluoride into enamel

To compare both quantitatively and qualitatively, the efficacy of dielectrophoresis to diffusion on the uptake of fluoride by enamel.

A 1.23% APF gel was applied to 16 bovine incisor specimens for 20 minutes by dielectrophoresis or diffusion. Absorption and penetration were evaluated by wavelength dispersive spectrometry.

Fluoride concentrations in the diffusion group were significantly higher than baseline readings at 10 and 20 microm depths; fluoride concentration in dielectrophoretically treated teeth was significantly higher than the diffusion group at 10, 20, and 50 microm (ANOVA/Student-Newman-Keuls post hoc, P = 0.05). Significantly higher fluoride uptake was found with dielectrophoresis compared to passive diffusion at 10, 20, and 50 microm depths (paired t-test, P = 0.05). Dielectrophoresis doubled fluoride uptake in the superficial layers compared to passive diffusion, and drove the fluoride significantly deeper with an uptake six times higher than diffusion at 50 microm depth. Dielectrophoresis enhanced penetration and increased uptake of fluoride on average by 600% at 50 microm. The amount of fluoride delivered at 50 microm was equivalent to long-term exposure of prophylactic fluoride. With proper polarizing frequencies, dielectrophoresis could enhance fluoride delivery into tooth enamel at higher penetration depths and concentrations than diffusion.