Comparison of remineralization between conventional fluoride application and iontophoresis

Objectives: The aim of this in vitro study was to compare the effects on the remineralization by the conventional fluoride application (CFA) and the iontophoresis.

Methods: Sixty bovine enamel specimens were embedded in acrylic resin with the labial surfaces exposed. All the specimens were immersed into a carbopol demineralization solution for 2 days at 37°C to produce a caries-like lesion on the specimen surface. The specimens were randomly divided into 3 groups: no fluoride treatment, CFA, and iontophoresis. The experimental groups were respectively divided into 2 different subgroups (1.23% APF gel, 2% NaF solution). The control group was not treated with fluoride and was placed in a remineralization solution (RS) for 5 days. However, all the experimental groups were immersed in the RS for 1 day after the fluoride treatment for 4 minutes. This cycle was repeated 5 times. The Vickers surface micro-hardness number (VHN) of all the specimens was measured using microhardness tester and the specimen surfaces were observed by scanning electron microscope (SEM), confocal laser scanning microscope (CLSM). The results were analyzed using one-way ANOVA followed a Tukey's test at a significance level of 0.05 (SPSS Inc., Chicago, USA).

Results: According to the fluoride application method, although the iontophoresis groups showed higher VHN (difference in mean = 4.83±6.77) than the CFA groups, there were no significant differences between two fluoride application methods. After the fluoride application, the 1.23% APF gel with the iontophoresis group (154.63±16.47) showed the best remineralization (p<0.05). The 2% NaF solution with the CFA group (114.06±12.44) showed the lowest remineralization (p<0.05). These results were also confirmed by SEM, CLSM.

Conclusion: The iontophoresis for applying the fluoride did not show any significant superiority to the conventional fluoride application in terms of the remineralization on early caries lesion.

This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MOST) (No. R13-2003-013-01004-0).