Enhanced penetration of fluoride particles into bovine enamel by combining dielectrophoresis with AC electroosmosis

Abstract

Fluoride deposition into the pores of enamel is necessary at high concentrations to reduce enamel demineralization and with a high degree of penetration to account for loss by ingestion. Current diffusion and electrochemical methods are inadequate for effectively transporting fluoride greater than 20 μm into enamel. The study explores the coupling of dielectrophoresis (DEP) and AC electroosmosis (ACEO) to selectively concentrate fluoride particles from fluoride gel excipients and enhance their penetration into enamel. By measuring the frequency response of approximately 10-μm-sized sodium fluoride particles in an aqueous gel media, appropriate frequencies for positive DEP, negative DEP, and ACEO are identified. An assembly composed of two cross-planar interdigitated electrode (IDE) arrays with open slots is driven successively by fields at appropriate frequencies to drive fluoride particles through the slots of the IDE and into the enamel pores using a combination of DEP and ACEO methods. Fluoride uptake and penetration of 1.23% acidulated phosphate fluoride gel into bovine tooth enamel at various depths is measured using wavelength dispersive spectrometry to compare deposition by diffusion, DEP, and DEP plus ACEO. Fluoride levels in all DEP groups were significantly higher than diffusion groups at depths 10 and 20 μm. The highest fluoride concentrations at 10, 20, 50, and 100 μm depths occur under deposition conditions combining DEP with ACEO. Fluoride levels at 50 μm were equivalent to long-term prophylactic exposure. These methods may potentially benefit populations at high risk for development of caries and periodontal disease, including underserved children and disparate groups.

Enhanced Delivery of F−, Ca2+, K+, and Na+Ions into Enamel by Electrokinetic Flows

“…This ubiquitous source of organic acids in the oral cavity makes acid penetration into enamel nanopores a highly frequent event, which could lead to demineralization and ultimately tooth decay (Thylstrup et al 1994;Marcenes et al 2013; Sheiham and James 2014; Sheiham and James 2015). The deterioration of enamel hydroxyapatites could be hindered by transporting relevant ions deep into enamel sublayers, while current caries prevention fluoride technology is limited to a diffusion process that delivers ions very slowly, at unknown rates, and to the outmost surface layer (Anderson and Elliott 1992;Shellis 1996;Dorozhkin 2012;Ivanoff et al 2013).…”

“…As an alternative, using electric fields to facilitate the transport of materials into enamel to improve dental health has been investigated by different groups in recent years. Ivanoff and coworkers used dielectrophoresis to transport fluoride and carbamide peroxide into the enamel to the depth of 50 to 100 µm by applying an alternating current (AC) electric field (Ivanoff et al 2011;Ivanoff et al 2012;Ivanoff et al 2013). Iontophoresis was used by Pitts and coworkers to deliver remineralizing agents into minor enamel surface lesions (Pitts et al 2009;Pitts and Wright 2018).…”

Review: Electric field driven pumping in microfluidic device

“…for separation, concentration, manipulation, and sensing. For instance, ACEO pumping is combined with dielectrophoresis for the collection of cells [122] and particles [123], separation of colloids [124], rotation [125] and manipulation [126] of particles in a microfluidic chip. Similarly, by combining with other microfluidic-based actuation technique, ACEO pumping is used for separation and concentration [127-130] and detection [131-134].…”

Improved mineralization of dental enamel by electrokinetic delivery of F- and Ca2+ ions

“…The dissolution of enamel due to caries and erosion could be hindered by transporting relevant ions to hydroxyapatite solubility (such as Ca 2+ and F − ) deep into normal (sound) enamel sublayers. Nevertheless, existing caries prevention methods are limited to diffusion process that delivers ions very slowly, at unpredicted rates, and to the outermost enamel layer only [9][10][11][12] . The application of electrokinetic ow (EKF), compared to dielectrophoresis 10,13,14 and iontophoresis 15 , has shown a greater promise in enhancing material transport into the pores of normal enamel 16 .…”