Biomimetic Mechanism of Action of Fluoridated Toothpaste Containing Proprietary REFIX Technology on the Remineralization and Repair of Demineralized Dental Tissues: An In Vitro Study

Abstract

Objectives: This in vitro study aimed to characterize the mineral content and surface and cross-sectional morphology of enamel and dentin tissues treated with a 1450 ppm fluoride-containing toothpaste with REFIX technology.

Materials and methods: Bovine enamel blocks (n = 5) were obtained (4 × 4 × 6 mm), demineralized (artificial caries lesion), and treated (pH cycling and brushing with the toothpaste). During the pH cycling, which lasted for 7 days (demineralization and remineralization took 6 and 18 hours, respectively), the enamel was brushed for 5 minutes using an electric toothbrush before being immersed in a remineralizing solution. The dentin blocks were acid-etched for 2 minutes (0.05 M citric acid, pH 1.8) to expose the dentinal tubules (n = 5). Morphological analysis of the dentin was performed immediately and after 7 days of brushing with the dentifrice, and compared with the control group. The specimens were then cross-sectioned. The surface and cross-sectional micromorphology were assessed using scanning electron microscopy (SEM). The elemental analyses (weight%) were determined with an energy-dispersive X-ray spectroscopy (EDS).

Results: The toothpaste with REFIX technology remineralized and repaired the surface enamel effectively. The elemental analysis also demonstrated that treating the enamel with the toothpaste formed a silicon-enriched mineral layer on the enamel surface. Elemental analysis of the enamel cross-sections showed that the toothpaste induced a mineral change. The results were also consistent in the dentin, where the dentinal tubules were progressively occluded until there was complete occlusion after 7 days.

Conclusions: We prove the biomimetic mechanism of action of fluoridated toothpaste containing proprietary REFIX technology for obtaining silicon-enriched, remineralized and repaired dental tissues.

Fig. 1

Figure 1 ( A ) shows a representative scanning electron micrograph of the enamel surface (magnification 50x); above the line represents the control demineralized area; the area below the line represents the remineralized treated area. Figure 1 ( B ) shows a representative area of the demineralized enamel. Figure 1 ( C ) shows a representative area in which the enamel was remineralized and regenerated. Figure 1 ( D ) shows the cross-sectional area of the control, demineralized enamel half. Figure 1 ( E ) shows a representative scanning electron microscope (SEM) photomicrograph image the cross-section of enamel block in which a mineralized layer is formed at the treated enamel surface.

Fig. 2

Representative scanning electron micrographs of the enamel cross-sections and the elemental mapping at different depths (from surface area A to the deepest area D). EDS detected stronger silicon signals at the surface area (0.56 weight%), which increased right below the mineralized layer formed at the enamel surface (C, 0.77 weight%), and decreased in the deepest area (D, 0.24 weight%). The amounts of sodium, phosphorus, and calcium also varied as a function of the depth.

Fig. 3

Scanning electron micrographs of the morphological analysis of the surface and cross-sectional areas of the dentin: ( A ) shows a representative scanning electron micrograph of the demineralized dentin with open tubules. ( B ) shows a representative scanning electron micrograph of the dentin immediately after brushing with the toothpaste with occluded dentinal tubules. ( C ) shows the dentin surface in which a mineralized layer was formed after 7 days of treatment. ( D ) shows the scanning electron micrograph of the treated dentin with a majority of occluded tubules after 1 week of treatment. ( E ) shows a scanning electron micrograph of the mineralized layer formed at the dentin surface, demonstrating the presence of silicon (6.70 weight%), fluorine (0.90 weight%), calcium (1.60 weight%), and phosphorus (0.46 weight%) in the elemental analysis.